1. Field of the Invention
This invention generally relates to fluid-filled inflatable chambered prosthetic implants and methods of fabrication thereof, which are employed to volumetrically alter, replace, expand, or augment tissues, and, more particularly, to adjustable implants formed from self-sealing elastomeric membranes.
2. Description of Related Art
Breast reconstruction after mastectomy presents challenges as a result of tissue loss and scarring. The tight chest-wall skin can often require skin grafting to replace lost tissue. Expanding the skin is a more desirable method to avoid skin grafting. Temporary skin expanders can be utilized but require eventual removal and replacement with the appropriate permanent implant. The multiple surgical procedures are difficult for the patient and introduce additional risks and costs. This invention will make a single surgery possible with slow expansion of the tissues remaining after the mastectomy. The implant can potentially be adjusted at any time, even years after the initial surgery.
Many breast implants are commercially available. A single chamber design is most common, and is available in a variety of fixed volumes to produce a range of sizes and shape characteristics from about 80 to 800 cubic centimeters. As used herein, “chamber” refers to the interior portion of a breast implant, which is enclosed by an outer shell or membrane. As is known by those skilled in the art, the interior portion of an implant may also be referred to as a lumen. The implants are generally filled with silicone gel or saline. Viscoelastic silicone shells of all implants are very similar in composition, but vary in thickness, texture, and surface treatments. There are very significant differences with respect to the filling materials. The silicone gel implants generally have more natural properties, with fewer noticeable edges and rippling effects. The viscosity of the silicone gel reduces fluid motion that results in these beneficial properties. The silicone gel filling the implant may alter over time to become firmer, softer, and change in elasticity, depending on its composition. Historically, a major complication has been gel bleed leading to capsular contraction and tissue toxicity to the patient. Many gel-filled implants have additional barrier coatings or layers to lessen the diffusion of silicone into the tissues. Diffusion can be reduced, but not eliminated.
Saline implants were developed to eliminate complications related to fluid bleed. Saline is biocompatible and able to be absorbed without tissue toxicity complications in the event of a slow bleed or rupture of the implant. The low viscosity of saline allows for significant fluid motion leading to deformation of the fluid-filled shell. The wave and ripple motion is often visible through the overlying tissue. This is a more significant complication in cases where there are not significant amounts of tissue surrounding the implant. The deformation of the viscoelastic membrane can cause the surrounding tissue to scar and contract, distorting and hardening the feel of the implant. Saline implants are often placed deep under muscle tissue of the chest and slightly overfilled to prevent complications.
Shell coatings and texturing have been developed to reduce capsular contraction, with reasonable success. The variable surface treatments all work by enabling tissues to adhere and distribute forces responsible for contracture. The materials utilized to form, coat, and fill the implants have resulted in a wide variety of available designs. Size and shape alone produce many options. The designs become more involved when multi-chamber and variable volumetric designs are considered. Variability of volume during surgery allows for adjustments to be made for general size and symmetry. Access ports and valves are used to inflate or deflate the implant. In some cases, the filling tube is left in place for a short period to allow for further adjustments post-surgery. This adjustability is a desirable and, often, a necessary feature in the case of tissue expanders.
Multi-chamber implants predominantly consist of an inner chamber and an outer chamber filled with silicone, saline, or a combination of both. The combination of chambers allows for greater variability in size and shape characteristics. Currently available models have a double membrane, double chamber design, in which an outer chamber has a fixed volume of gel and an adjustable inner chamber is filled with saline. These implants provide a very natural appearance and feel with the added advantage of temporary adjustability. These more complex designs have been found to be less resistant to shear forces in areas where there are junctions between the membranes and valve port.
Implants are intended to safely provide a natural feel and appearance, while minimizing leakage and contracture. Therefore, there is a need for an implant that achieves necessary performance and safety. It would also be beneficial for the implant to remain adjustable following surgery, to allow for appropriate correction if the patient physically changes or has different expectations after the surgery is completed. Such adjustments must be performed in a safe manner, without increasing risk to the patient or requiring additional surgical procedures. The implant should also be configured to adjust for minor leakages over time. The implants and methods of formation thereof provided herein address some or all of these needs.